Hi all,
As promised in my last post, I have finally finished designing and building a cheap interface to connect ham radios or any other audio device that does not share audio common ground to a PC, including a PTT interface. Price should be around $17 or 60 NIS. The control is done using a USB interface, so unlike most ham radio hardware that uses serial connections, this one is plug and play in modern PCs. The neat thing is that it uses them same commands as a RigBlaster. So this interface works out of the box with common ham radio programs like Echolink and Svxlink. The interface should also work with soundmodem which can be used for X.25 packet digital communications, without any extra hardware (I am still trying to get this to work). This interface could also be used to connect to other devices that don’t share a common ground. For example like phone lines.

Parts you will need

TTL USB Serial interface – The main part is a simple CP2102 $4 controller that can be percussed from ebay. It simulates a serial device, meaning you can still work with older pieces of software with it. Note though you need to solder a cable from the RTS pin on the board, because normally they don’t come with a pre-made pin.

Audio line isolation transformer – This can be easily salvaged from any old dial-up modem. That’s how I get mine, it seems to be much easier to get them off old modems than finding them in electronics shops, plus they are so easily identifiable (just make sure not to break the contacts when you take them out, happened to me twice). If you can’t find any old dial-up modems you can get it from ebay. (more…)